Trans-Bis(N,N-diethylethylenediamine)nickel(II) dibromide

Abstract

The structure of the title compound, [Ni(C6H16N2)2]Br2 or [Ni(Et2en)2]Br2 (Et2en is asymmetric N,N-diethyl­ethylene­diamine), containing an NiII atom (site symmetry ) in square-planar NiN4 coordination, is described and contrasted with related structures containing NiII in octa­hedral coordination with axial X − ligands (X − = variable anions). The dialkyl­ated N atom has an appreciably longer bond length to the NiII atom [1.9666 (13) Å] than does the unsubstituted N atom [1.9202 (14) Å]. The Ni—N bond lengths in [Ni(Et2en)2]Br2 are significantly shorter than corresponding values in tetra­gonally distorted [Ni(Et2en)2 X 2] compounds (X = −O2CCF3, OH2, or −NCS), which have a triplet ground state. The electronic configuration in these axially ligated [Ni(Et2en)2 X 2] compounds populates the metal-based d x 2 -y 2 orbital, which is Ni—N anti­bonding in character. Each Et2en ligand in each [Ni(Et2en)2]2+ cation forms a pair of N—H⋯Br hydrogen bonds to the Br− anions, one above and below the NiN4 square plane. Thus, a ribbon of alternating Br− pairs and [Ni(Et2en)2]2+ cations that are canted at 65° relative to one another is formed by hydrogen bonds.